The present invention relates to toilets, and particular to pressure toilets with siphon assist.
Achieving an effective flush of a toilet when the bowl is filled with feces, toilet paper, and other solids can be difficult, particularly with a low water consumption toilet. It is common, again especially with some low water consumption toilets, for consumers to flush the toilet twice or more to clean the bowl to their satisfaction. This is not only frustrating and time consuming for consumers, it subverts the environmental and water conservation efforts in many jurisdictions that regulate water consumption, which in many areas may be no more than 1.6 gallons (6.1 liters) of water per flush.
Conventional toilets have a bowl and a storage tank, usually formed in one or two main pieces. A serpentine passage, typically referred to as a “trapway”, is positioned behind and below the bowl as conduit for the contents of the bowl to the waste plumbing lines of the building. While the precise configuration of a toilet's trapway varies, all generally include an up leg, which is normally filled with water to “trap” sewer gases downstream thereof, so as to prevent them entering the building interior. Water is maintained in the bowl and the up leg of the trapway by an arched weir or dam of the trapway that is elevated above the opening of the bowl. The trapway thus also helps retain water in the bowl prior to flushing.
During a flush cycle, water and waste within the bowl are passed up the up leg over the dam, down a down leg and through an outlet to plumbing lines. The mechanism for creating a flush is different when comparing pressure flush toilets and gravity flush toilets. The latter makes use of the air in the down leg and the pressure head in the up leg forced over the dam to establish a siphon in the trapway that draws the water and waste from the bowl and out of the trapway. As the bowl is emptied, air enters the trapway and breaks the siphon, and fresh water from the tank refills the bowl.
In pressurized toilets, which use one or a combination of line pressure, tank stored pressurized water, or sump pumped water, a pressurized stream of water is injected into the trapway or the bowl to blow the bowl contents through the trapway. A siphon of the type produced in conventional gravity toilets is typically not used in pressurized toilets. However, some pressurized toilets, (e.g. U.S. Pat. No. 6,219,855) do purport to use a siphon as well.
It is difficult to achieve consistent sustained siphon in the trapway of conventional pressure toilets. This is because the trapways of conventional pressure toilets are typically designed differently than in gravity toilets. In particular, the trapways in pressure toilets usually have a large area down stream from the up leg. This enlarged area accommodates the liquid and bulk waste material that is evacuated rapidly from the bowl and into the trapway by the water jet. Without it, water and waste may be forced back through the up leg and back into the bowl, which may defeat an effective flush.
Unfortunately, the large space downstream from the up leg thus makes achieving and sustaining a siphon difficult. One reason for this is that the large sectional area in the blow out region of the trapway requires more liquid and waste to fill it. Another reason is that air in the down leg prior to initiation of the flush cycle may be forced back into the up leg through a part of this enlarged region not occupied by the evacuating water and waste.
Hence, improvements are desired in pressurized toilets with respect to the use of siphons.